On 2017年03月22日 22:16, Michael S. Tsirkin wrote:

On Tue, Mar 21, 2017 at 12:04:46PM +0800, Jason Wang wrote:

quoted

We used to dequeue one skb during recvmsg() from skb_array, this could
be inefficient because of the bad cache utilization and spinlock
touching for each packet. This patch tries to batch them by calling
batch dequeuing helpers explicitly on the exported skb array and pass
the skb back through msg_control for underlayer socket to finish the
userspace copying.

Tests were done by XDP1:
- small buffer:
   Before: 1.88Mpps
   After : 2.25Mpps (+19.6%)
- mergeable buffer:
   Before: 1.83Mpps
   After : 2.10Mpps (+14.7%)

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
  drivers/vhost/net.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++----
  1 file changed, 60 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9b51989..53f09f2 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c

@@ -28,6 +28,8 @@
  #include <linux/if_macvlan.h>
  #include <linux/if_tap.h>
  #include <linux/if_vlan.h>
+#include <linux/skb_array.h>
+#include <linux/skbuff.h>
  
  #include <net/sock.h>
  

@@ -85,6 +87,7 @@ struct vhost_net_ubuf_ref {
  	struct vhost_virtqueue *vq;
  };
  
+#define VHOST_RX_BATCH 64
  struct vhost_net_virtqueue {
  	struct vhost_virtqueue vq;
  	size_t vhost_hlen;

@@ -99,6 +102,10 @@ struct vhost_net_virtqueue {
  	/* Reference counting for outstanding ubufs.
  	 * Protected by vq mutex. Writers must also take device mutex. */
  	struct vhost_net_ubuf_ref *ubufs;
+	struct skb_array *rx_array;
+	void *rxq[VHOST_RX_BATCH];
+	int rt;
+	int rh;
  };
  
  struct vhost_net {

@@ -201,6 +208,8 @@ static void vhost_net_vq_reset(struct vhost_net *n)
  		n->vqs[i].ubufs = NULL;
  		n->vqs[i].vhost_hlen = 0;
  		n->vqs[i].sock_hlen = 0;
+		n->vqs[i].rt = 0;
+		n->vqs[i].rh = 0;
  	}
  
  }

@@ -503,13 +512,30 @@ static void handle_tx(struct vhost_net *net)
  	mutex_unlock(&vq->mutex);
  }
  
-static int peek_head_len(struct sock *sk)
+static int peek_head_len_batched(struct vhost_net_virtqueue *rvq)

Pls rename to say what it actually does: fetch skbs

Ok.

quoted

+{
+	if (rvq->rh != rvq->rt)
+		goto out;
+
+	rvq->rh = rvq->rt = 0;
+	rvq->rt = skb_array_consume_batched_bh(rvq->rx_array, rvq->rxq,
+						VHOST_RX_BATCH);

A comment explaining why is is -bh would be helpful.

Ok.

Thanks
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